Effects of etchant concentration and duration on the retention of orthodontic brackets: an in vivo study

Etching of enamel before the bonding of orthodontic attachments is usually done with a solution of 37% H3PO4 for 60 seconds. The purpose of this study was to evaluate the effects of etchant concentration and duration on the clinical retention of bonded orthodontic attachments. Two randomly selected groups of orthodontic patients participated in the study. In both groups, teeth in contralateral quadrants, excluding the molar teeth, were bonded. In the first group, 158 teeth were etched with a solution of 37% H3PO4 for 60 seconds, and 155 teeth were etched with 37% H3PO4 for 15 seconds. In the second group, 196 teeth were etched with 37% H3PO4 and 196 teeth with 15% H3PO4, both for 60 seconds. Conventional edgewise mechanotherapy was used in both groups of patients. After 24 months of treatment, in the first group, 8 brackets were dislodged when etched with 37% H3PO4 for 60 seconds and 9 when etched with 37% H3PO4 for 15 seconds. In the second group, 6 brackets were dislodged when etched with 37% H3PO4 for 60 seconds and 13 were dislodged when etched with 15% H3PO4 for 60 seconds. Reducing the etching time of 37% H3PO4 from 60 seconds to 15 seconds or reducing the acid concentration from 37% to 15% H3PO4 applied for 60 seconds had no significantly different effect on the retention of bonded orthodontic attachments. The results suggest that the reduction of etchant concentration and the duration of etching in orthodontic bonding should be considered.